1. Field of Invention
The invention is directed to downhole tools for use in acid treatment and fracturing in oil and gas wells, and in particular, to downhole tools having a sleeve capable of being moved to initially force an acid from the tool and into a formation of a wellbore and, without any additional intervention from the surface other than the continued pumping downward of a fracturing fluid, force the fracturing fluid from the tool and into the formation.
2. Description of Art
Fracturing or “frac” systems or tools are used in oil and gas wells for completing and increasing the production rate from the well. In deviated well bores, particularly those having longer lengths, fracturing fluids can be expected to be introduced into the linear, or horizontal, end portion of the well to frac the production zone to open up production fissures and pores therethrough. For example, hydraulic fracturing is a method of using pump rate and hydraulic pressure created by fracturing fluids to fracture or crack a subterranean formation.
In addition to cracking the formation, high permeability proppant, as compared to the permeability of the formation can be pumped into the fracture to prop open the cracks caused by a first hydraulic fracturing step. For purposes of this disclosure, the proppant is included in the definition of “fracturing fluids” and as part of well fracturing operations. When the applied pump rates and pressures are reduced or removed from the formation, the crack or fracture cannot close or heal completely because the high permeability proppant keeps the crack open. The propped crack or fracture provides a high permeability path connecting the producing wellbore to a larger formation area to enhance the production of hydrocarbons.
Prior to the pumping of fracturing fluids into the wellbore, it is sometimes desirable to pump acids or other fluids into the formation to remove debris and other matter that could interfere with the pumping of the fracturing fluids into the formation. To do so, downhole tools are generally re-oriented or reconfigured between the steps of pumping acid and pumping fracturing fluid. Alternatively, the ports from which the acid is pumped into the formation is different from the ports in which the fracturing fluid is pumped. Thus, without additional intervention, the efficacy of the fracturing fluid is reduced because it is not being pumped into the location where the acid was previously pumped.